Introduction to tables

Tables are essential objects in a database because they hold all the information or data. For example, a database for a business can have a Contacts table that stores the names of their suppliers, addresses, and numbers. Because other database objects depend so heavily on tables, you should always start your design of a database by creating all of its tables and then creating any other objects. Before you create tables in Access, consider your requirements and determine all the tables that you might need. For an introduction to planning and designing a database, see Database design basics.

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Overview

A relational database like Access usually has several related tables. In a well-designed database, each table stores data about a particular subject, such as employees or products. A table has records (rows) and fields (columns). Fields have different types of data, such as text, numbers, dates, and hyperlinks.

1. A record: Contains specific data, like information about a particular employee or a product.

2. A field: Contains data about one aspect of the table subject, such as first name or address.

3. A field value: Each record has a field value. For example, Contoso, Ltd. or .

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Table and field properties

Tables and fields also have properties that you can set to control their characteristics or behavior.

1. Table properties

2. Field properties

In an Access database, table properties are attributes of a table that affect the appearance or behavior of the table as a whole. Table properties are set in the table's property sheet, in Design view. For example, you can set a table's Default View property to specify how the table is displayed by default.

A field property applies to a particular field in a table and defines one of the field's characteristics or an aspect of the field's behavior. You can set some field properties in Datasheet view. You can also set any field property in Design view by using the Field Properties pane.

Data types

Every field has a data type. A field's data type indicates the kind of data that the field stores, such as large amounts of text or attached files.

A data type is a field property, but it differs from other field properties as follows:

• You set a field's data type in the table design grid, not in the Field Properties pane.

• A field's data type determines what other properties the field has.

• You must set a field's data type when you create the field.

  You can create a new field in Access by entering data in a new column in Datasheet view. When you create a field by entering data in Datasheet view, Access automatically assigns a data type for the field, based on the value that you enter. If no other data type is implied by your input, Access sets the data type to Text. If needed, you can change the data type by using the Ribbon.

Examples of automatic data type detection

The following table shows how automatic data type detection works in Datasheet view.

If you enter:

Access creates a field with a data type of:

John

Short Text

http://www.contoso.com

You can use any valid Internet protocol prefix. For example, http://, https://, and mailto: are valid prefixes.

Hyperlink

1

Number, Long Integer

50,000

Number, Long Integer

50,000.99

Number, Double

.389

Number, Double

12/67

The date and time formats recognized are those of your user locale.

Date/Time

December 31,

Date/Time

10:50:23

Date/Time

10:50 am

Date/Time

17:50

Date/Time

$12.50

The currency symbol recognized is that of your user locale.

Currency

21.75

Number, Double

123.00%

Number, Double

3.46E+03

Number, Double

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Table relationships

Although each table stores data about a different subject, tables in an Access database usually store data about subjects that are related to each other. For example, a database might contain:

• A customers table that lists your company&#;s customers and their addresses.

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• A products table that lists the products that you sell, including prices and pictures for each item.

• An orders table that tracks customer orders.

Because you store data about different subjects in separate tables, you need some way to tie the data together so that you can easily combine related data from those separate tables. To connect the data stored in different tables, you create relationships. A relationship is a logical connection between two tables that specifies fields that the tables have in common. For more information, see Guide to table relationships.

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Keys

Fields that are part of a table relationship are called keys. A key usually consists of one field, but may consist of more than one field. There are two kinds of keys:

• Primary key    A table can have only one primary key. A primary key consists of one or more fields that uniquely identify each record that you store in the table. Often, there is a unique identification number, such as an ID number, a serial number, or a code, that serves as a primary key. For example, you might have a Customers table where each customer has a unique customer ID number. The customer ID field is the primary key of the Customers table. When a primary key contains more than one field, it is usually composed of pre-existing fields that, taken together, provide unique values. For example, you might use a combination of last name, first name, and birth date as the primary key for a table about people. For more information, see adding or changing a table&#;s primary key.

• Foreign key    A table can also have one or more foreign keys. A foreign key contains values that correspond to values in the primary key of another table. For example, you might have an Orders table in which each order has a customer ID number that corresponds to a record in a Customers table. The customer ID field is a foreign key of the Orders table.

The correspondence of values between key fields forms the basis of a table relationship. You use a table relationship to combine data from related tables. For example, suppose that you have a Customers table and an Orders table. In your Customers table, each record is identified by the primary key field, ID.

To associate each order with a customer, you add a foreign key field to the Orders table that corresponds to the ID field of the Customers table, and then create a relationship between the two keys. When you add a record to the Orders table, you use a value for customer ID that comes from the Customers table. Whenever you want to view any information about an order's customer, you use the relationship to identify which data from the Customers table corresponds to which records in the Orders table.

1. A primary key, identified by the key icon next to the field name.

2. A foreign key &#; note the absence of the key icon.

Do not add a field if you expect that each unique entity represented in the table might require more than value for the field. Continuing the preceding example, if you want to start tracking orders placed by your customers, you do not add a field to the table, because each customer will have more than one order. Instead, you create a new table to store orders, and then create a relationship between the two tables.

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Benefits of using relationships

Keeping data separated in related tables produces the following benefits:

• Consistency    Because each item of data is recorded only once, in one table, there is less opportunity for ambiguity or inconsistency. For example, you store a customer's name only once, in a table about customers, rather than storing it repeatedly (and potentially inconsistently) in a table that contains order data.

• Efficiency    Recording data in only one place means you use less disk space. Moreover, smaller tables tend to provide data more quickly than larger tables. Finally, if you don't use separate tables for separate subjects, you will introduce null values (the absence of data) and redundancy into your tables, both of which can waste space and impede performance.

• Comprehensibility    The design of a database is easier to understand if the subjects are properly separated into tables.

Plan your tables with relationships in mind. You can use the Lookup Wizard to create a foreign key field if the table that contains the corresponding primary key already exists. The Lookup Wizard creates the relationship for you. For more information, see Create or delete a lookup field.

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See Also

Create a table and add fields

When we think of data visualization, it is the charts and graphs that come to mind. But did you know tables are a form of data visualization as well? 

Tables play an essential role in presenting data. Unlike charts and graphs, tables can accommodate a great deal of detailed information, including numeric values, labels, descriptions, and additional contextual data. Plus, they offer flexibility of customization and adaptation to different structures & data formats, such as text, numbers, dates, and categorical variables. And the best advantage of it all, they are understood by a wider range of audiences.

While encoding charts may require some skill, most people are accustomed to reading and interpreting tabular information, which can enhance comprehension and ease of understanding.

Let&#;s understand further why tables can sometimes be advantageous over charts.

• Precise numerical values Tables provide an exact representation of numerical values that can be helpful when specific figures are important for analysis and decision making. This is particularly relevant when dealing with financial data, scientific measurements, or precise calculations.

• Detailed comparisons Tables make it easier for readers to perform detailed comparisons between different data points or categories, enabling them to examine and compare values more effectively. This is specially useful when dealing with multiple variables or when the data requires deeper scrutiny.

• Textual information Tables are a great way to display both qualitative (text) and quantitative(numerical) data, which can help readers gain deeper knowledge about the topic. They can include additional details such as descriptions, explanations, or extra information about data that may be difficult to convey using charts alone.

• Data lookup and reference When users need to quickly locate specific information or reference specific data points, tables can be more efficient and effective than charts. The organized layout of tables makes it easier to scan and find information, specially when the data in the table is well-structured and logically arranged.

It&#;s important to note though, the decision to display information through tables or charts depends on the nature of the data, the intended audience, and the goal of the presentation.

In many instances, using a combination of both tables and charts can offer the best of both worlds, allowing for a comprehensive understanding of the data through multiple visual and tabular representations.

ANATOMY OF A TABLE

• Title The table title provides a concise summary of the data presented in the table and helps users quickly understand the table&#;s purpose and context. To differentiate the title from the rest of the table, use a prominent background or font color, for font size, to make it easy on the users to understand the table&#;s information hierarchy.

• Subtitle Subtitle includes additional descriptive text that provides more context or information about the data being presented. It typically appears below the table&#;s title and above the column headers or the table body. Subtitles could include clarification of the data, such as time period, methodology used, units of measurement, key finding. Subtitle formatting option would be similar to the table title.

• Column Headers Column headers located at the top of each column identify the type or category of data contained in that column. You may format them differently, such as use different font, bold typeface or a different background color, to distinguish them from data cells.

• Row Headers Row headers are situated at the leftmost side of the table. They label each row and help identify specific data points or categories associated with the rows.

• Rows / Columns / Cells Rows represent horizontal records, columns represent vertical attributes, and cells are the individual units within the table that contain data values at the intersection of rows and columns.

• Totals ( Rows or Columns ) In some instances, data tables may include a row or column at the bottom or rightmost side to display the totals or summary statistics for each respective column or row. This helps users quickly assess overall trends or aggregated values.

• Key/Legend If the table incorporates specific symbols, abbreviations, or color coding, a key or legend may be included to provide explanations for these visual cues. This ensures that users can accurately interpret the data and understand any special representations used in the table.

Guidelines to Format Tables

A well formatted table really enhances the readability, clarity, and understanding of the data. Mostly, they are easier to interpret.

Looks understand the basic guidelines of table formatting by fixing the table below.  

Let&#;s start fixing:

• Use Clear and Consistent Titles, Subtitles and Column Headers Clearly label each column header to indicate the content or variable being represented and ensure that table titles are descriptive enough to give users a basic idea of the table&#;s purpose.

• Apply Gridlines Sparingly Use gridlines sparingly to avoid cluttering the table. Consider using subtle gridlines or removing them entirely if they don&#;t add significant value to the table&#;s readability.

• Format Titles As described earlier, you can use a bold typeface or different font or background coloring to format titles properly and differentiate them from the rest of the table.

• Align Data Appropriately Align the data within each column consistently. Generally, numeric data is right-aligned, while text or descriptive data is left-aligned. This alignment makes it easier for viewers to scan and compare values within a column. You can left-align titles & subtitles as well if you wish (like below) , but it is more of a personal preference.

• Format Numbers for Readability When dealing with numbers in particular, the larger they become, the harder it becomes to read, increasing the chances of confusion. As best practice, use a thousand separator to differentiate thousands from hundreds, or millions from thousands, and improve the readability of the table.

• Provide Units of Measurement: Units of measurement helps viewers understand the scale and context of the data. You may include units in the column headers or as a separate row to provide clarity and avoid confusion. In the table below, the $ (dollar) sign has been included in the Revenue column header.

• Adjust Row Height & Column Widths

  Excessively wide or narrow cells that can make the table appear unbalanced or lead to data truncation. Use row height & column width adjustments to accommodate the content appropriately and ensure optimal readability. Also, use sufficient white space between rows and columns to create visual separation and make data more scannable.

• Group Related Data If your table has multiple sections or categories, consider grouping related data together visually. You can achieve this by using horizontal lines to separate sections or by using different font styles or background colors for distinct groups of rows.

• Consider Sorting and Highlighting Sort the data in a logical order to facilitate understanding. Use formatting techniques such as bolding, italics, or color to emphasize specific data points or highlight important information However, use these formatting elements sparingly and consistently to avoid distracting from the overall table.

Other formatting considerations

• Alternate Row Shading Consider applying alternating row shading to improve readability and distinguish between rows. This can be achieved by using different background colors for even and odd rows or by using subtle shading patterns.

• Limit Decimal Places Depending on the precision and significance of the data, consider limiting the number of decimal places displayed. This avoids unnecessary clutter and ensures readability. Precision will depend on context & sensitivity of numbers as well.

• Consider Additional Visual Enhancements Depending on the nature of the data and the purpose of the table, you may consider including additional visual enhancements such as icons, arrows, or trend indicators to provide quick visual cues or aid interpretation.

Let&#;s remember&#;

Tables are a great visualization tool because they provide a structured format for displaying information in rows and columns, making it easy for users to compare and analyze the data. However, it is also worth noting that the choice of visualization you use will ultimately depend on the nature of the data and the insights you want to convey.

While tables are effective for certain types of data, other visualizations tools like charts or graphs will be more suitable for presenting trends, distributions, or relationships.

But as far as tables are concerned, just make sure your formatting choices align with the purpose and audience. Keep the table design clean and uncluttered. Remove unnecessary gridlines, excessive text, or elements that do not add value. Overall, simplify the table layout to focus on the essential information ensuring that the data is presented in a clear, organized, and visually appealing manner.

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